Two women and a man finished fueling the boat a little before 11:45 a.m. and were just pulling away from the Jantzen Beach Gas Dock when an explosion blew the engine's cover into the air, said Lt. Michael Silva, Portland Fire and Rescue spokesman.

Flames began to spread soon after and the three people, who have not been identified, leapt from the watercraft and swam back to the dock.

The engulfed boat continued drifting away from the dock, was extinguished by firefighters and later pulled from the river.

A leaking fuel line is believed to have factored into the explosion, said Silva, but the incident is still under investigation.